Modern radio communication receivers typically utilize a radio frequency (RF) amplifier to achieve maximum sensitivity. The RF amplifier has a limited dynamic range, which can cause clipping of strong radio signals. Clipping generates spurious frequencies that can interfere with reception and demodulation of desired frequencies. For portable battery-powered receivers, which can operate from a single 1.5-volt cell, the dynamic range limitation can be severe--especially near the end of battery life when battery voltage drops to about 1.0 volt.
To prevent the RF amplifier from being overloaded by high signals, various automatic gain control (AGC) systems have been incorporated to control signal amplitudes. A problem that has been associated with such AGC systems has been that the AGC systems themselves have required more than 1.0 volt for operation. Conventional ways of solving the problem have included adding voltage multiplier circuits or using multiple-cell batteries to increase the operating voltage. Neither of these solutions is desirable in terms of cost and efficiency.
Thus, what is needed is an AGC system that can maintain receiver operation without signal overload, and that requires no more than 1.0 volt for reliable operation.